Automatic telephone system



April 24, 1928. 1,667,385

E. E. JONES AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. 9, 1921 3Sheets-Sheet 1 Eui-wm EJ021515 6% z. w-

r 3 Sheets-Sheet 2 E. E. JONES AUTOMATIC -TELEPHONE SYSTEM Gngmal FlledFeb 9 1921 ii 11 I April 24, 1928.

April 24, 1928. 1 1,667,385

E. E. JON E 5 AUTOMATIC TELEPHONE SYSTEM Original Filed Feb. '9, 1921 3Sheets-Sheet 3 -1iwan Ur 137mm E. June 565%. W

Patented Apr. 24, 1928.

EDWIN E. J'OLNES, OF CHICAGO, ILLINOIS,

Assienon, {BY MEsNn ASSIGNMENTS, mo

AUTOMATIC ELECTRIC INCL, OF CHICAGO, ILLINOIS, zAHCQRPOR'ATION OF DELA-WARE.

' AUTOMATIC TELEPHONE SYSTEM Application fil ed February 9, 1921;SerialNo; 443,654. Renewed June 15, 1927.

The ,present invention relatesto automatic telephone s stems but isconcerned more particularly with small systems which are conif monlyknown as private automatic eX-' feature of this character which iscommonly known as conference calling. "This is an arrangement to enablean official of a com pany having a private automatic exchange to talk toa number of his employees simultaneously; in other words a numberoftelephone lines may be connected together for conference purposes.Hitherto in arrangements of this character it has been necessary tomaintain in use trunk lines and switches for each telephone line duringthe conference. This invention contemplates a scheme of thisnaturewherein the trunlnlines and switches used during a conferenceare reducedto a minimum. v

The particular manner in which this and other results are accomplishedwill be explained fully hereinafter, reference being had totheaccompanying drawings; Refer ring now to the accompanying drawingscomprising Figs. 1 to 3, in order for thedrawings to be understood best,Fig. 1 should be placed over Fig. 2, andi-Fig. 3 should be placed underFig. 2.

Referring first to 7 shown two substations of the usual automatictype,.each having a rotary line switch of wellknown constructionindi'vidual'thereto. These line, switches are indicated by referencecharacters (land 0, and in com mon with a plurality of other lineswitches have access to trunk lines leading to connector switches, oneof which is shownat D, Fig.2. This connector is of the usual Strowgervertical and rotary type and has the usual set of contacts arranged inten rows or levels. 011 the first eight levels the switch D andotherlocal switches have the functions ofordinary connectors except in oneinstance which exception is on the conference number. On thetenth levelthe switch D operates as an ordinary selector switch. On the ninth levelin addition to Fig. 1,}at A and A are a short distance apart in a cityserved'by a public manual exchange. Ojne of these fac tories is suppliedwith telephone service by l the private automatic exchange under diskcussion while the other l'factory is supplied wlth telephone serviceanother; private" automatic exchange of the-same type. Thetenth level inthe private automatic exchange in factory No. l is reserved for trunklines leading to the private automatic exchange, 1 1n factory No. 2,while the ninthlevelris used."

for trunk lines extending to the public mane ual exchange. i

From the above description the fwiring ioo of the banks of the connector-D. will be readily understood, 'Bank contacts 18814 O, inclusive, are,the terminals of conductors leading to the local substation A, while-thebank contacts l421 l4, inclusive, are terminals of a lineleadingtosubstation A. Bank, contacts 134 136, tinclusive, reliiresentvthe,

g8!) conference,numberwhich it wlll be assumed is the number 60. Theconductorsleading from this-set of banlrcontacts terminate an auxiliaryconnector switch Fig. Bank contacts 130-132, inclusive, are ter manualexchange, while contacts 125-127,.inelusive, are terminals of a'trunkline "extending to the private automatic exchange at factory No. 2. Allthe sets ofcontacts above described are multiplied in the usual man 90minals of a trunl: lineleading tothe public;

nor into all localconnector switches similar to the switch D. The switchH is used only for conference purposes andis an ordinary v 1100 mgaccess to local snbscrlbers llnes only and well known Strowgerconnectorhav- Tlie bank contacts in the connector switch H in which the localsubscribers lines terminate are joined to the multiple between the localcon1iectors, but before .bei-ngso joinedv one line conductor of eachsubscriber who is entitled. to conference service is passed throughthewinding of a ser1es:r elay,these being represented in the drawings at320 and 327, which are the relays individual to the lines leading tosubstations A and A, respectively.

Having briefly described the apparatus in the system, a detailedexplanation of its operation will now be given. For this purpose it willbe assumed that the subscriber at substation A desires to hold aconference. Under these conditions this subscriber will remove hisreceiver and call the regular local number of the first subscriberdesired in the conference, prefixing the digits of the conference number60. l v hen the receiver is removed at substation A a circuit is closedfor the line relay 13 of the line switch C over the line conductors 11and 12 in series. Upon operating, relay 13 at its armature 2O closes acircuit which includes the switching relay 14: and the stepping magnet15 in series, and at its armature 21 connects the test wiper 26 to theabove circuit at a point midway between the switching relay and the saidstepping magnet. The operation now depends upon whether the trunk linewith which the .wipers of the line switch C are associated is or is notbusy. If the trunk line is busy the test contact with which the testwiper 26 is in engagement will be grounded, and as a result theswitching relay 1 1 will be short circuited and the stepping magnet 15,being supplied with direct ground by way of the said test wiper, willoperate as a buzzer to advance the switch wipers step by step in searchof an idle trunk line. It will be assumed, however, that when the callis initiated the wipers of the line switch C are standing upon the bankcontacts shown in the drawings, and it will be further assumed that thetrunk line extending from these contacts is idle. Under thesecircumstances the test contact 29 will have no ground potential on itand when the receiver is removed the energization of the line relay 13is followed immediately by the energization of the'switching relay 14.It may be stated at this point that the switching relay is of very highresistance so as to prevent the operation of thestepping magnet 15 atthis time. As a result of the energization of the switching relay 14,the line conductors 11 and 12 are disconnected from the line relay 13and from ground, respectively, and are extended by way of armatures 16and 1S and their front contacts, wipers 25 and 27, bank contacts 28 and30, trunk conductors 38 and 10, armatures 75 and 7 8 and their backcontacts, to the upper and lower windings of the double wound line relay50 of the local connector 1).

When the calling line is extended to the switch D as above described theline relay 50 enargizes over the line circuit and completes a circuitfor the slow acting release relay 51. Upon energizing, relay 51 preparesthe operating circuits of the connector D at its armature 66, and atarmature 67 establishes a holding circuit which extends from ground Gfront contact and armature 67, release trunk conductor 89, armature 17and its front contact, and through the winding of the switching relay 11 andthe stepping magnet 15 to battery. The above circuit is completedbefore the slow acting line relay 13 has had time to deenergize andserves to maintain the switching relay 14 energized throughout theconnection. Ground is also extended by way of the private normalconductor 31 to multiply connected test contacts in the from intrusionin the ordinary manner.

The calling subscriber may now operate his calling device in accordancewith the first digit. of the conference number, or the digit 6.Six'interruptions are thereby pro duced in tl e line circuit of relay 50which deenergizes a corresponding number of times, each time completinga circuit extend ing from ground G, armature and its back contact,armature 66 and its front contact, off normal springs 69and 68, throughthe winding of the slow acting series relay 52 and the winding of thevertical magnet 100 to battery. The above is the circuit over which thefirst impulse is transmitted. At the first upward movementof the shaftthe off normal springs are shifted and the circuit for the verticalmagnet is completed over a new path which is the same as the onepreviously tracedexcept that it includes the oil normal springs 69 and77, and armature and its front contact, slow acting relay 52 being now'in an operated position. By the operation of the vertical magnet 100 theswitch wipers 120122, inclusive, are raised step by step untilthey are)lZICGd opposite the sixth level of bank contacts. The slow actingseries relay '52, which is energized in series with the vertical magnet,maintains its armature attracted throughout. the vertical movement ofthe switch and at the end of the vertical operation deenergizestransferring the operating circuit to the rotary magnet- 102.

The calling subscriber may now operate hiscalling device in accordancewith the second digit of the conference number namely, the digit 0. Teninterruptions are thereby produced in the circuit of the'line relay 50which operates in response thereto and at each retraction of itsarmature completes a circuit extending as follows: Ground G, armature 65and its back contact, arn'iature 66 and its front contact, off normalsprings 69 and 77, armature 70 and its back contact, normally closedsprings controlled by relay 57, armature 99 and its back contact, andthence through the winding of the rotary magnet 102 to battery. Magnet102 operates to rotate the wipers 120-122, inclusive, into engagementwith the'tenth set of con banks of the connector switches, whereby thesaid line is'protected tacts'in the sixthflevel which, it will beassumed, are the bankcontacts 131136, in- ClHSIVG. The-slowacting relay58 is ener gi'z ed in multiple'with the rotary magnet and-operates toconnect the test wiper 4121' Whenthe springs 83and8ei are brought intoengagement a circuit iscompleted extending from ground'on release itrunkconductor 39 by way of armature 96 and its back contact,

th'roughsprings ea andSS, and through npperwinding of relay 56 tobattery. Relay 56 operates-to establish a locking circuit for itselfatits armature Bland at armatures 80 and "82 prepares a :point in thedialling oircuit of the auxiliary connector H. If the line is busy theoperation of. the springs 83 and 84; will have no function at this timeex cept as above stated. Supposing this to be the case ground will bepresent on the test contact 135 engaged by the test wiper 121. A circuitwill thereby be completed extend ing from the said groundedtest contactby way of test wiper 121, normally closed springs controlled by relay59, armature 9O 3 and its front contact, back'contact and, armature .93,and thence through the winding of the test relay 57 to battery. Uponoper- .ating, the relay 57 establishes a locking circuit for itselfatarmature 85, opens the rotary rnagnet circuit by the operation ofarmature 86, and at armature 87 places the busy tone upon the lower lineconductor, of the calling subscriber thereby notifying him that, for thepresent the conference number is inaccessible. The calling subscriberwill therefore replace his receiver upon the switchhook, therebyreleasing the switches C and D in a manner to be explained here--inafter.

l Iowever, it will be assumed in the present-case that the conferencenumber was idle when connection thereto was attempted. Under thesecircumstances no ground will be-present on the test contact 135 and testrelay 57 will not be energized. A circuit is then completed upon'thedeenergization of the slow acting relay 58, extending from ground onrelease trunk conductor 89, ar-

mature 85 and its back contact, through the energizes over this circuit,and establishes a locking circuit for itselfat armature 9'7 and atarmatures 95and 1L0 prepares another point in the dialling circuit tothe auxiliary connector H4 Uponenergizing, relay 59 at armature 96 alsoremoves :t-he ishort circuit around the relay 55$ A circuit isthencifective 1 extending from ground on FlElGflSG trunk conductor 89,through the winding of relay 55,-camsprings 84: and 83, and throughtheupper winding ofrelay 56 to battery. iitelay 55, upon energizing,completes the dialling circuit to the auxiliary connector H. Thiscircuit includes the lll16:l'6l2iyf250 which is energized over a circuitextending from ground G through the lower winding iof relay 250,conductor 156, bank contact 134, wiper 120,:front contactaud armature95, through the winding oflow resistanceseries relay 58, front contactand arn'iature 7:5, thence overthe line conductor B8 of the substationA, through the transmitter-landre.- ceiver of the said substation, lineconductor 40, armature T8 and its front contact, front contact andarmature 82, armature 110 and its front contact, wiper .122, bankcontact, 136, conductor 158,'through the upperwind ring of the linerelay 1 5.0 to battery.- -,,Y-Relays 53 and250 energize over thiscircuit. f-Re-' lay 53 at lts armature 76 H1al11t21l]1S"1tlle C1P- cuitofthe slow acting releasere'lay .51 of thelocal connector D in anoperated lJOSl-r tion thereby preventing the release of the switch D andmaintaining thelineswitchG in an operated position; Relay 250, uponenergizing,completes thecircuit of-the slow acting release relay 252 ofthe auxiliary connector H. c i i i i The calling subscriber atsubstation A may now call the remaining two digits ofthe desired localsubscribers number. When the calling device is operated for thefirstdigit of the subscribers number a series of interruptionsfi-sproduced in the line circuit of the linerelay 250 of theconnector H.Bee. lay 250 operates in responsetheretoand sends a corresponding seriesof impulses-over. a circuit extending fromground G, by Way of armature265 and its back contact, arma ture 269 and its front contact, ofinormal. springs 272 andf270, through the winding of the slowacting relay253 and-through the vertical inagnet QGO to battery, The above is thecircuitover which the first impulse is transmitted. Upon the'firstvertical step of the shaft the oft normal springs are shifted and theremaining impulses to the vertical magnet are sent over a differentci.rcuit which is the same as theone previously traced except thatitincludes the off normal springs 27 2 and 27 3 and armature 275 and'its front, contact, relay 253 being now in an operated position. Themagnet 260 op erates to raise the wipers 290-292, inclusive, stepby'step until they standflopposite the level of bankcontacts inwhichcthe desired subscribers line is located. I The slow acting v relay253 is energized'in serieswith-the yertical magnet 260,,maintains itsarmature at tracted throughout the vertical operation of Ground G",armature 265 and its back contact, armature 269 and its front contact,off normal springs 272 and 278, armature 275 and its back contact, backcontact and armature 283, armature 288 and its back contact, and thencethrough the winding of the rotary magnet 261 to battery. Magnet 261 operates to rotate the switch wipers 290-292, inclusive, into engagementwith the set of bank contacts associated with the line of the desiredsubscriber, which it will be assumed are bank contacts 298300,inclusive, in'which the line of the subscriber at substation A isterminated. The slow acting relay 256 is energized in multiple with therotary magnet and operates to connect the test wiper 291 to the testrelay The further operation of the connector 'H depends upon whether ornot the line of the desired subscriber is or is not busy. if busy atthis time, a ground potential will be present on the test contact 299. Acircuit is thereby completed extending from. the said grounded testcontact by way of the test wiper 291, armature 284C and its frontcontact, and through the winding of the test relay 255 to battery. Uponenergizing, re

lay 255 establishes a locking circuit for itself at armature 282 and atarmature 281 connects the busy tone to the line of the subscriber atsubstation A. Upon hearing this tone the calling subscriber will knowthat the line he desires is busy and he will replace his receiver upontheswitchhook, thereby releasing the switches in a manner which will bedescribed fully hereinafter.

Let us assume now that the line of the subscriber at substation A wasidle when connection thereto was attempted. Under these circumstancesthere will be no ground potential present on the test contact 299engaged by the test wiper 291. A circuit is thereupon completedfollowing the deenergization of the slow acting relay 256 which extendsfrom ground on release trunk conductor 263 by way of armature 282 andits back contact, upper winding of the switching relay 257, back contactand armature 28 1,'test wiper 291, bank contact 299, con ductor 151,conductor 35, through the winding of the switching relay 32 of the lineswitch C and through the winding of the stepping magnet 83 to battery.Relays 257 and 32 operate over this circuit. Due to a mechanicalinterlocking device controlled by the armature of the line relay 31, theswitching relay 32 is only operated enough to clear the line of thesubstation A from its normal battery and ground connections in the lineswitch G. Relay 257, upon operating, establishes a locking circuit for,itself at its armature 287, opens the rotary magnet circuit at armature288, and at armatures 285 and 289 completes the ringing circuit. Ringingcurrent will flow over a circuit extending from the generator V, backcontact and armature 280, armature 289 and its front contact, Wiper 292,bank contact 300, through the winding of relay 327, and the condenserassociated therewith in multiple, conductor 152, conductor 36,switchhook springs, ringer and condenser of the substation A, conductor34,,conductor 150, bank contact 298, wiper 290, front contact andarmature 285, armature 278 and its back contact, and thence through theupper winding of the ring cut-0E relay 254: to battery. Ringing currentis intermittently applied to the above traced ringing circuit until thesubscriber at substation A removes his receiver from the switchhook. Therelays 827 and 25s are so constructed that they do not respond toalternating current and hence will not operate over the ringing circuit.

When the subscriber at substation A re moves his receiver a path fordirect current is provided over the line circuit thereby energizing therelays 327 and 254. Relay 25 i upon energizing, establishes a lockingcircuit for itself at armature 279 and at and 336 and their frontcontacts to extend the line of the subscriber at substation A intoconnection with the conference holding trunkcomprising conductors 340and 341. The calling subscriber at substation A will inform thesubscriber at substation A that a conference is to be held. It will benoticed that while relay 327 is included in the line circuit between thetwo subscribrs its inclusion will have no effect on the transmission ofvoice currents because a path for talking current is provided by thecondenser associated with relay The calling subscriber will then hang uphis receiver thereby openings the line circuit of relay 250 and also thecircuit of the series relay 53. Both these relays deenergize therebyopening the circuit of the slow acting release relays 51 and 252 intheir respective switches, relay 51 upon deenergizing, completing therelease magnet circuitof the connector D at the sainetime removingground from the holding circuit of the line switch C and relay 2" 2 upondefrom intrusion in the ordinary manner and over the following circuit:Ground through the lower winding of thecommon talking impedance 325,front contact and armature 336 through the winding of relay 327 and iover the line conductors of the called substation, armature 333 and itsfrontcontact,

, and through the upper winding of the impedance 325 to battery. Atarmature 337, relay 327 also maintains ground on private normalconductor 151 of the substation A thereby protecting the line of thesubscriber at the same timemaintaining the switching relay 32of the lineswitch C in its operated position. V

The "calling subscribed at substation A will now remove his receiverand, in identically the same manner as above described, call anotherlocal branch exchange subscriber by means of a local connector and theauxiliary connector H. This operation will now be briefly described.WVhen the-receiver is removed at substation A the line switch G operatesas before described to se- 1 lcctan idle trunk terminating in a localconnector which it will be assumed is the connector D. v V p When thecallingdevice at substation A is operated for the digits of theconference number 60 the line relay controlsthe operation of thevertical magnet 100 in stepping the switch wipers 120122, inclusive,opposite the sixth level of bank contacts. hen the last digit of theconference number isdialled the line relay 5O responds to theinterruptions in its line circuit and con trols the operation of therotary magnet 102 i in rotating the switch wipers into engagement withthe conference number. When this occurs relays 56, 59 and 55 "againenerto complete the circuit of the line relay 250 of the auxiliaryconnector I-l.

The calling sijib'scriber may now operate his calling device inaccordance with the first digit of the next local subscribers number.The line relay 250 operates, sending a corresponding series of impulsesto the vertical magnet 260 in series with'the-slow act'- relay 253 inthe same manner ;'as previously described. Magnet 260 operates to raisethe wipers290-292, inclusive, step by stop, until they are placedopposite the level of bank contacts in which th'enext local subline islocated. The slow acting re rgized in serieswith the res:

tical magnet and maintains its armature attracted throughout thevertical operation of theswitclr and atthe termination of the verti a1movement deener-giz es, thereby transferring theoperating circuit to therotary, magnet 261. 3

hen the last digit of the local subscribers number is called therotaryma-gnet 26-1 under the control of the line relay 250 operates torotate the switch wipers into en; gagen'ient witlrthe set of -ba'nlrcontacts in which the desired subscribers line is tere initiated. 'Ifthis line is busy the connector H will operate in the usual manner togive the busy tone to the calling subscriber. If the line is idle theswitching relay 257 will energize and complete the ringing circuit,Ringing current is then intermittently projected over the line circuitof this subscriber in identically the same manner as va -sidescribed inthe connection with the subscriber at substation A.

lVhen this called subscriber answers the ring out off relay 25s and therelay silnilarto relay 327 in series with the line circuit: will beenergized, relay 25etestablishing a locking circuit for itself andcompleting the; talking connection, the relay similar to 327 beinoperated to transfer the line of the called subscriber onto theconference holding trunk. After informing this called subscriber that aconference is to be held the calling subscriber will replace hisreceiver upon the switchhool; thereby initiating the release ofsubscribers in the conference, for "the reason that he has nowbeenplaced in telephonic coi'rnection' with the conference holding trunkcomprising conductors 3 10 and 3&1 by means of the energization of theseries relay similar to 327 in the line of the subscriber last called.it

. When the conferenceis terminated each subscriber by placing hisreceiver upon the switchhookj severs his connection with the conferenceholding trunk, the relays 32.0,

327 and similar relays being deenergized' upon theassociated calledsubscribers replac ing their receivers upon the switchhook. hen thecalling subscriber replaces his receiver upon the switchhook he willrelease the operated switches C, D, andIIin manner before described.

Having described the'process of up conference ,the' manner in which alocal' connection is coinplete d wil l sown-e sciibedi For this purposeas sinned that the subscriber at substation A de sires to call thesubscriber at substation A. hen the receiver is removed at'substation Athe line switch C operates in the'usnal manner to select an idle trunkterminating in a local connector switch which it will be assumed is theconnector D. The line relay of the connector D will be energized overthe line circuit completing the circuit of the slow acting release relay51. Relay 51 energizes preparing the operating circuits of the switch Dat armature 66 and at armature 67 establishing a holding circuit for theline switch C.

l/Vhen the calling device'at substation A is operated for the firstdigit of the desired number of the line relay 50 responds to theinterruptions in its line circuit and at each retraction of its armaturecompletes a circuit extending from ground G by way of armature 65 andits bacl: contact, armature 66 and its front contact. off normal springs69 and 68, through the winding of the series relay 52, and the windingof the vertical magnet 100 to battery. Upon the first step of the switchthe otl' normal springs are shifted and the impulses are sent to thevertical magnet over a different circuit which includes the elf normalsprings 69 and 7? and armature 0 and its front contact relay 52 beingnow in an operated position. Magnet 100 operates to raise the wipers 120122, inclusive, step by step until they are placed opposite the level ofbank contacts in which is located the line of the desired subscriber.The slow acting series relay 52 is energized in series with the verticalmagnet and re mains so throughout the vertical operation of the switch.At the termination of the vertical movement the slow acting relay 52deenergizes and transfers the operating circuit to the rotary magnet102.

lVhen the'callinp; device at substation A is operated in accordance withthe last digit of the subscribers number another series of interruptionsis produced in the circuit of relay 50. Relay 50 operating in responsethereto sends a series of impulses to the rotary magnet 102 in multiplewith the slow acting relay 5S. Magnet 102 operates to rotate the switchwipers into engagement with the set of contacts in which are terminatedthe conductors of the desired subscribers line and which, we willassume, are the bank con tacts 1&2 14 1, inclusive. As before, relay 58being energized in multiple with the rotary magnet 102 operates toconnect the test wiper 121 to the test relay 5?. 1f the line of thesubscriber at substation A should happen to be busy at this time aground potential will be present on the test contact 1 13.

Supposing this to be the case, acircuit is then completed extending fromthe said grounded test contact by way of the test wiper 121, normallyclosed springs controlled by relay 59, armature 90 and its frontcontact, back contact and armature 93, and through the winding of thetest relay 57 to battery. Upon operating, relay 57 establishes a lockingcircuit for itself at armature 85 and at armature 87 places the busytone on the calling subscribers line. The calling subscriber uponhearing this tone will know that the line is busy and will replace hisreceiver thereby causing the release of the connector D and the lineswitch 0 in the usual manner.

It will, however, be assumed that the line of the subscriber atsubstation A was idle when connection thereto was attempted. Under thesecircumstances there will be no ground present on test contact 1&3. Acircuit isthen completed upon the deenergization of the slow actingrelay 58 extending from ground on release trunk conductor 39, armature85 and its back contact, through the lower winding of the switchingrelay 59, back contact and armature 90, normally closed springscontrolled by relay 59, test wiper 121, test contact 143, conductor 151.conductor 35, and through the winding of the switching relay 32 and thestepping magnet 38 to battery. Relays 32and 59 operate over thiscircuit, relay 32 operating, as before, to disconnect the line of thesubscriber at substation A from its normal battery and groundconnections in the line switch C. Relay 59 upon operating, establishes alocking circuit for itself at armature 97 places ground on the privatenor mal conductor 151 at armature 98 and at armatures 95 and 110completes the ringing circuit. Ringing current is then intermittentlyapplied to the line of the substation A until the subscriber thereatresponds by removing his receiver from the switchhoolr. lVhen thisoccurs the ring cut oil relay 56 energizes establishing a lockingcircuit-for itself at armature 81 and at armatures 80 and 82 opening'theringing circuit, and at the front contacts of these armatnres completingthe talking connection. Couriers-a tion may now be carried on betweenthe subscribers at substations A and A battery being supplied to thecalling subscriber from the winding of the line relay 50 and to thecalled. subscriber from the windings oi the back bridge relay 54L Vhenthe COIIYQISttion is terminated both subscribers will replace theirreceivers upon the switchhoolt, the replacement of the receiver at thecalling substation A initiating the release of the line switch C andconnector D as previously described,

Having described the process of setting up a local connection, themanner in which a trunk connection to the public manual exchange iscompleted will now be explained, after which a description will be givenof the process of establishing a trunk connection to a" subscriber in"the other private automatic exchange which'is located at factory No. 2.p

As before stated the trunk lines extending to the main exchangeterminate in the ninth level; It follows therefore, that in order toconnect with one of these trunk lines the digit 9 must be called. Thesubscriber. atsu'bstation A who desires to connect with the mainexchange willtherefore remove his receiver and operate his callingdevicein accordance with the digit 9 When the receiver is removed the lineswitch 6 operates as before described to extend the associated line to atrunk line terminating in an idle local connector switch.

ssumin iavtre on1ec Y 'isi -A ,tl tl c 1 toiD dle and is selected foruse. When connection is extended thereto the line and release relays 50with the same results.

be accomplished by any suitable cam arrangement'. A convenient way is tomount the spring assembly comprising springs 105-108,. inclusive, justabove the top of the shaft so that spring 106 will be operated by thecup spring casing mounted at the upper extremity of the switch shaft.switch isoperated opposite the ninth level the spring 106 willbeoperated and when the switch shaft. is raised opposite the tenth levelboth springs 106 and 108 will be actuated;

To proceed, thejslow actingseries 1"elay 52is energized during thevertical operat on 01' the switch and for an instant there 'when theninth and tenth level sha'tt springs 105 and 106 are closed on the ninthvertical stcpra circuit is completed extending as follows: Groundonrelease trunk conductor 39. by way of shaft controlled springs 105 and106, springs 109, armature 73 and its front contact, back contact andarmature 93, and through the winding. of the test relay 57 to battery.Upon energizing, relay 5'5. establishes alockingcircuit for itself atarmature and at armature 86"prepares the rotary I magnet circuit. At thetermination of the vertical movement of the shaft the slow actingrelay52 deenergizesan d a circuit is thereby completed extending fromground on release trunk conductor 39 by way of shaft controlled springs105 and 106, springs 109, armature 73 and its back contact, armature 86and its front contacnarmat'ure 99 and its back contact, and through thewinding of l Vhen the atter and,

the rotary magnet 102 to battery. Relay 58 is energized in multiple withthe above circult ,of the rotary magnet: 'Ma-gnet' 1020perates to rotatethe switch wipers 120122, I

on whether or not thetrunk line with which 7 the switch wipers are inengagement is or is not busy. If busy, a ground potential will bepresent on the test, contact engaged by the wiper 121'; A circuit isthereby com pleted extending from the said grounded test contact by wayof test wiper 121, normally closed springs controlled by relay 59,

armature 90 and its front contact, backcon- 1 tact and armature 93,and'thr'o'ugh thewindingot the test relay 57 to battery. Relay 57energizes and again completes the rotary magnet circuit. Relay 57' and1nagneti102 will operate alternately" until an idle trunk line is foundwhich, we will assume, is the trunk line terminating in, bank contacts130132, inclusive. lVhen the switch wipers are rotated into engagementwith this set of bank contacts no ground will be present on testcontact131. Then upon the deenergization of the slow acting'relay 58 a crcuit is completed extending from groundon release trunkconductor-39,armature 85 and its back contact, lower winding of the switching relay59, had; contact and armature 90, normally closedsprings controlled 'byrelay 59,

. test; wiper 121, test contact 131, through resistance R to battery.Relay 59" energized over this circuit and establishes a lockingcircuitefor itself at armature Wand at armatur'es 95 and1'10 completes aringiugcircuit. Ringing current is then automatically pro jected outover the trunk line the sameas in the case of the called local line andthe ring downdrop or other signalling .device at the manual switchboardin the public exchange is operated in .t'heusual manner. lVhen theoperator plugs in to answerthecall the ring cut oil relay 56 isoperated, disconnects the ringing currentand completes the talkingconnection. local station in the main exchange may he completed by theoperator through the medium of any suitable means which need not beexplained herein.

The operation of the local connector I) when usedfor trunking to thesecond private automatic exchange is-thc same as in thecase justdescribed'in so far as the selection-of an 1dle trunk 18 concerned, butsince theconnecv tion in the private automatic exchange must becontrolled automatically the circuits of the switch D are alteredsuitably in order'to permitthe switch to operate as a series repeater'for the purpose of repeating impulses loo The connection to the desiredover the selected trunk line extending tothe private automatic exchangeat factory No. 2. The operation which takes place when connection isextended to the second private automatic exchange will now be brieflyexplained.

Since the trunk lines extending to the pri vate automatic exchange atfactory No. 2 terminate in the tenth level the digit to be called is thedigit 0. Assuming that a subscriber at substation A desires to call aparty in the second private automatic exchange, when the receiver isremoved the line switch G operates to extend the line of the callingsubscriber to an idle connector D. V iVhen the calling device isoperated for the digit 0, ten interruptions are produced in the linecircuit of the relay 50 which deenergizes a corresponding number oftimes whereby controlling the vertical magnet 100 in raising the switchwipers 120122, inclusive, step by step until they are placed oppositethe tenth level. Upon the tenth vertical step of the switch the springs105 and 106. and 107 and 108 are shifted into engagemen As before, theslow acting relay 52 is energized in series with the vertical magnet andmaintains its armature attracted throughout the vertical movement of theswitch and for an instant thereafter. When the springs 105 and 106 arebrought into engagement a circuit is thereby completed for the testrelay 57 which energizes establishing a locking circuit for itself atarmature 85 and preparing the rotary magnet circuit at armature 86. Uponthe termination of the vertical movement of the switch relay 52deenergizes. A circuit is then completed for the rotary mag net 102 inmultiple with the slow acting relay 58. Magnet 102 operates to rotatethe wipers 120122, inclusive, into engagement with the first set ofcontacts in the tenth level and to also break the locking circuit ofrelay 57. the operation of springs 107 and 108 a circuit is completedextending from ground on release trunk conductor 39, armature 06 andits'back contact, shaft controlled springs 107 and 1.08, and through theupper winding of the ring out oft relay 56 to battery. Relay. 56operates as before, establishing a locking circuit for itself at itsarmature 81, and at armatures and 82 preparing a point in the repeatingcircuit. If the trunk line with which the switch wipers are associatedis busy ground'willbe present on the test contact thereof and the relay5'? will be again energized to complete the rotary magnet circuit. Thealternate operation of relay 57 and magnet 102 will continue until anidle trunk line is found which, we will assume, is the trunk lineterminating in the bank contacts 125-127, inclusive. W hen the switchwipers are rotated into engagement with this set of contacts ground willnot be present on the test contact 126 and a circuit is completedextending from ground on release trunk conductor 39 by way of armature85 and its back contact, lower winding of relay 59, back contact andarmature 90, normally closed springs controlled by relay 59, test wiper121, test contact 181, and thence through re sistance R to battery.Relay 59 upon operating, establishes a locking circuit for itself atarmature 97, at armatures and 110 prepares another point in therepeating circuit, and at armatures 9-6 removes short circuit from relay55. A circuit is then eifective extending from ground on release trunkconductor through the winding of relay 55, shaft controlled springs 107and 108, and through the upper winding of the.

ring cut off relay 56 to battery. Upon operating, relay 53 completes therepeating circuit in the same manner as was described when the switch Dwas operated to seize the auxiliary connector H on the conferencenumber. Relay 53 is energized in series with this repeating circuit andoperates as before to maintain the slow acting relay 51 in an operatedposition as long as the calling subscriber atsubstation A maintains hisreceiver off the switch-hook. It will be seen that the subscriber atsubstation A by op erating his calling device will produce a.

series of in erruptions in the line relay circuit of the incoming switchin the private automatic exchange at their factory No. 2, and theconnection is thereby completed to the subscriber in private automaticexchange No. 2, in the usual manner. It will also be seen that only atwo conductor trunk' is necessary between the two private automaticexchanges for the reason that the series relay 53 in the connector Dmaintains the switches C and D in their operated position.

In case a call is attempted by way of either the ninth or the tenthlevel of the connector D and all the trunks in the called level arebusy, the trunk selecting operation of the switch D continues until thewipers 120422, inclusive, are rotated out of engagement with the lastset of bank contacts.

This occurs upon the eleventh rotary step 1 and, at'this time, a cam onthe switch shaft shifts spring 109 out of engagement with its lowercontact and into engagement with its upper contact, thereby opening thecircuit of the rotary magnet and closing a circuit to maintain busyrelay 57 energized so as to give the usual busy signal to the callingsubscriber.

Having described the invention what is considered to be new and desiredto have protected by Letters Patent will be pointed out in the appendedclaims.

What I claim as my invention is:

1. In a telephone system, calling and called subscribers lines,automatip switches, tan

' a holding trunk, means whereby asubscriber ,on one of said callinglines may establish connections with a number ofsaid called s'ubscriberslines, a relay individual to theline of each called subscriber, and,means 'con trolled by the response of the SLIbSCliliGlflOil each of saidcalled li-nes for energizing; the

associated relay to place theassociated called. subscribers lineinconnectioni with the said holding trunk. V c

In a, telephone, system, calling subscribers line, automatic switches,ahol'ding,

trunk, a plurality ot called subseribefis lines, means under thecontrollofcthe subscriber on the said calling line for establishingconnections successively with each ofs ,id called subscribers lines, arelay individualto each of said called lines, means for, energizing,

each oi? said relays upon the response of its subscriber on theassociated called line, and

means controlled by each: relayfor connectins its associated calledsubsci iberslinet Q I I c scribe'r on said called line for placingthesaid holding trunk. V a I a In atelephone system, a. calling subscribersline, automatic switches,a holdingtrun-k, a plurality ofcalled.subscribers"lines,, means under the control of the subscriber on,

oneof said callinglines for establishingcon:

nections successively with each ofsai-dfcalled] ing, each ofrsaid relaysup on the response.

6. Ina telephone system, calling and called subscribers lines;,agutomatic' switches,

means whereby asubscriber ,on.,one of said calling linesmayestablish a"connection with alcall ed subscribers line tlii'o-ugli' a series ofsaid, automatic switches, a holding trunk,

means controlled bythelsubscriber on said:

called line forjplacing his line in connection-with the said holding,trunk, and means under the control of the subscriber on saidcallingjline for releasing said series of automatic switches while thesaid called subscribers line is maintained in connection with the saidholding trunk. 7. In a, telephone system, a calling subscribers line,automatic switches, called subscribers lines accessiblethere-to,meansunder the controlofthe subscriber on the said call ii'i'gline for, establishing ,connectionlwitl'i' one ofsa-id called lines byway of a series of said automat c switches, holtlliig tiilnli,

means controlled Jbythe response oftlie subsaid line in connection withthe said holding trunk, electrical means under the control of the,subscriber on said callingline for releasin'g all, of, said series ofautomatic.

' inn; his line from tliefsaid holding-trunk;

of the subscriber on its associated lin,e, neans; controlled by eachzrelay forfconnecting the associated called :subscribers line tothese-id holding trunk, and'meansi for, maintaining,

' from either connector switch, means whereby thesubscriberon. saidcalling lineima estab each relay energized to maintain the line oftheassociated CZIllGdJSUbSCllbQl in connection with the said holdingtrunk after the subscriber on said calling line replaces his receiver. e

a. In a. telephone system, a calling subscribers line, calledsubscribers lines, auto-- the response oteach oi? said calledsubsci-ibers for placing his line in connection with the linespreviously called independent of said automatic switches.

In a telephone system, a calling subscribers line, automatic switches,called subscribei's lines accessible to said switches, a holding; trunkcommon to all of said called subscribers lines, means under the controlof thesubscriber on the said calling line for establishing" a connectionwith a called subscribers line by way of said automatic switches, andmeans controlled by the response of the subscriber on the said calledline for placing his line in connection with the said holding trunk overa path independent of the said automatic switches.

sllllfltz telephone system, aacallingisubseriberls line, two automaticthe, other, a calledsubscribeids line accessible lHZLtlC switch, meanswhereby the subscriber on. said calling line may establish a secondconnection with the said called subscribers line by way of bothconnector switches, arain y individual to the line of the said calledsubscriber, and means for energizing said relay upon the response of thecalled sub;

scriber in the second connection only.

9. In a telephone system, a calling subscribcrs line, a. holding trunk,two automat-icconnector switches one of said switches accessible to theother, it called subscribers lineaccessible from either connectorswitch, means whereby the subscriberon said calling line may establish aconnection with the subscriber on said called line directly from saidfirst automatic switch, means whereby the subscriber on the said callingline may establish a second connection with the subscriber on saidcalled line by way of both connector switches, a relay individual to thesaid called line, means for energizing said relay upon the res ionse ofthe subscriber on said called line in the second connection,

, connector I sw tches, one of I said switches accessible to and meanscontrolled by the said relay for extending said called line intoconnection with the said holding trunk.

10. In a telephone system, two automatic connector switches, a lineaccessible to both switches, means for establishing a connection withsaid line by way of either switch, a relay individual to said line, andmeans for energizing said relay upon the response of the subscriber onsaid line when one of said connectors is used for the call, said relayremaining inert upon the response of the subscriber on said line whenthe other connector is used tor the call,

11. In a telephone system, two automatic connector switches, a lineaccessible to both switches, means for establishing a connection withsaid line by way of either switch, a relay individual to said line,means for energizing said relay upon the response of the subscriber onsaid line when one of said connectors is used for the call, said relayremaining inert upon the. response of the subscriber on said line whenthe other connector is used for the call, a holding trunk, and meanscontrolled by said relay tor connecting said line with said holdingtrunk.

12. In a telephone system, a line, two sets of terminals, the conductorsof said line be ing connected to both sets of terminals, a re lay, theconnection of said line to one set of terminals including said relay inseries, the connection of said line to the other set of terminalsexcluding said relay, a trunk, and means controlled by said relay forextending a talking connection from said line to said trunk.

13. In a telephone system, a line, a pair of branches for said line,step by step conl t. In a telephone system, a line, two sets ofterminals, the conductors of said line be ing connected to both sets oftern'iinals, a relay, the connection of said line to one set ofterminals including said relay in series, the connection of said line tothe other set of teri'ninals excluding said relay, another line, atrunk, means for connectin said other line, to said trunk, and meanscontrolled by said relay for extending a talking connection from saidtrunk to said first line.

15. In a telephone system, a plurality of lines each having two sets ofterminals, the conductors of said lines being connected respectively toboth sets of terminals, a relay for each line, the connections o't saidlines to one set of terminals including said relays in series, theconnections of said lines to said other set 01 terminals excluding saidrelays, a trunk line, a step by step automatic connector switch havingaccess to said first set of terminals, means for controlling saidconnector switch to connect with said terminals, and means controlled bysaid relay for extending talking connection between its associated lineand said trunk, independent of said connector switch.

Signed by me at Chicago, Illinois this 25th day of January 1921.

EDWIN E. JONES.

